In recent years, several techniques have been proposed for non-invasive determination of blood and tissue analytes, such as hemoglobin, glucose, bilirubin, cholesterol and others. Among the methods frequently used are methods that utilize light-matter interaction, especially of Red and Near-Infrared (RNIR) radiation through blood perfusion fleshy medium. Usually, the radiation consists of a plurality of wavelengths. Analyses of optical properties (absorption, scattering, transmission and/or reflection of different wavelengths) of blood, tissue or blood perfused fleshy medium assists in determination of the desired analyte concentration. For example, U.S. Pat. Nos. 5,111,817, 5,372,135, 6,266,546, and 6,473,632 disclose some of these techniques.